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cache ssd on home server perfomance


darkgeej

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Hi

im just building my first Unraid 6 server, and thought about

putting in a ssd for cache, but how much performance

does i give?

 

i got about 7 lan machines, and i run Plex server a lot  :)

 

So is it worth it for a homeuser ?

 

Plex runs way better on an SSD... I do it that way.. I actually have all my VM's and dockers running off an SSD cachepool.. And also use it as a regular cache drive..

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I have some questions about cache.

As far as I understand when you write new data, it gets written to the cache first and then dumped to the array later and then deleted from the cache.

But does data you access often gets copied back to the cache (so it works as read cache for data that earlier has been moved to array) or does you need to make shares that uses cache only to keep data on the cache and remember to take backup of this data?

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I have some questions about cache.

As far as I understand when you write new data, it gets written to the cache first and then dumped to the array later and then deleted from the cache.

But does data you access often gets copied back to the cache (so it works as read cache for data that earlier has been moved to array) or does you need to make shares that uses cache only to keep data on the cache and remember to take backup of this data?

 

Hope this clarifies it some.

 

When you write new data to a user share that is cache enabled it is written to the cache disk, later at a specified interval or when you manually invoke mover it is moved to the array.

 

The data will not be copied back to the cache for read reasons. This would actually just slow things down... (There is talk about accelerator drives which would use a script to cache frequently accessed and small files, but this isn't built in, and the reason this would speed things up is because the data is already on the cache before you know you want it...)

 

If you want to keep data on the cache, you have to make it cache only currently, this prevents it from being moved at all. This is the perfered method of running apps / dockers on unRAID currently.

 

Also you can take backups of this data, or you can configure a BTRFS RAID 1 Cache pool.

Link to comment

I have some questions about cache.

As far as I understand when you write new data, it gets written to the cache first and then dumped to the array later and then deleted from the cache.

But does data you access often gets copied back to the cache (so it works as read cache for data that earlier has been moved to array) or does you need to make shares that uses cache only to keep data on the cache and remember to take backup of this data?

 

Hope this clarifies it some.

 

When you write new data to a user share that is cache enabled it is written to the cache disk, later at a specified interval or when you manually invoke mover it is moved to the array.

 

The data will not be copied back to the cache for read reasons. This would actually just slow things down... (There is talk about accelerator drives which would use a script to cache frequently accessed and small files, but this isn't built in, and the reason this would speed things up is because the data is already on the cache before you know you want it...)

 

If you want to keep data on the cache, you have to make it cache only currently, this prevents it from being moved at all. This is the perfered method of running apps / dockers on unRAID currently.

 

Also you can take backups of this data, or you can configure a BTRFS RAID 1 Cache pool.

 

Any purpose for the Raid1 pool other than redundancy?

Link to comment

I have some questions about cache.

As far as I understand when you write new data, it gets written to the cache first and then dumped to the array later and then deleted from the cache.

But does data you access often gets copied back to the cache (so it works as read cache for data that earlier has been moved to array) or does you need to make shares that uses cache only to keep data on the cache and remember to take backup of this data?

 

Hope this clarifies it some.

 

When you write new data to a user share that is cache enabled it is written to the cache disk, later at a specified interval or when you manually invoke mover it is moved to the array.

 

The data will not be copied back to the cache for read reasons. This would actually just slow things down... (There is talk about accelerator drives which would use a script to cache frequently accessed and small files, but this isn't built in, and the reason this would speed things up is because the data is already on the cache before you know you want it...)

 

If you want to keep data on the cache, you have to make it cache only currently, this prevents it from being moved at all. This is the perfered method of running apps / dockers on unRAID currently.

 

Also you can take backups of this data, or you can configure a BTRFS RAID 1 Cache pool.

 

Any purpose for the Raid1 pool other than redundancy?

 

It enables you to have several ssd's combined into one cache drive... I have 4*  250GIG SSD, in effect is is giving me a 512GB raid 10-like storage pool.

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